Photoelectric conversion device

ABSTRACT

A transfer part of a photoelectric conversion device includes a first transfer region configured to transfer electric charge along a first line, a second transfer region configured to transfer the electric charge along a second line, a third transfer region configured to transfer the electric charge along a third line, a first transfer electrode, and a second transfer electrode. The third line is deviated from at least one of the first line and the second line. The third transfer region includes a first semiconductor region having a first impurity concentration, and a second semiconductor region having a second impurity concentration higher than the first impurity concentration. The second semiconductor region extends along the third line to be widened on the second transfer region side. The first semiconductor region is disposed on both sides of the second semiconductor region.

TECHNICAL FIELD

The present disclosure relates to a photoelectric conversion device.

BACKGROUND ART

As a conventional photoelectric conversion device, Patent Literature 1describes a solid-state imaging device as follows. That is, thesolid-state imaging device described in Patent Literature 1 includes animaging region that generates electric charge according to incidence oflight, and a transfer part (specifically, a vertical shift register, ahorizontal shift register, a corner register, and a multiplicationregister) that transfers the electric charge generated in the imagingregion. In the solid-state imaging device described in Patent Literature1, the horizontal shift register, the corner register, and themultiplication register extend to be bent in the curved corner register.

CITATION LIST Patent Literature

-   [Patent Literature 1] Japanese Unexamined Patent Publication No.    2010-177588

SUMMARY OF INVENTION Technical Problem

In the solid-state imaging device described in Patent Literature 1, thecorner register includes a plurality of transfer electrodes. Here, ifthe number of transfer electrodes of the corner register is reduced,since a difference between an inner width and an outer width in eachtransfer electrode increases, there is a likelihood that transfer ofelectric charge on an outer side of each transfer electrode will beinsufficient. In order to avoid that, if the number of transferelectrodes of the corner register is increased, the following problemsmay arise. That is, since an inner width of each transfer electrodebecomes smaller, there is a likelihood that a structure thereof will becomplicated and a yield thereof will decrease. Also, if the number oftransfer electrodes of the corner register is large, there is alikelihood that high-speed driving will be hindered due to increase inelectrical capacity, or power consumption will increase.

An objective of the present disclosure is to provide a photoelectricconversion device capable of reliably transferring electric charge whileavoiding increase in the number of transfer electrodes in such a case inwhich a direction of electric charge transfer or the like is changed ina transfer part.

Solution to Problem

A photoelectric conversion device according to one aspect of the presentdisclosure includes a photoelectric conversion part configured togenerate electric charge according to incidence of light, and a transferpart configured to transfer the electric charge, in which the transferpart includes a first transfer region configured to transfer theelectric charge along a first line, a second transfer region configuredto transfer the electric charge along a second line, a third transferregion configured to transfer the electric charge from the firsttransfer region side to the second transfer region side along a thirdline connected to the first line and the second line, a first transferelectrode disposed on the first transfer region, and a second transferelectrode disposed on the second transfer region, the third line isdeviated from at least one of the first line and the second line, thethird transfer region includes a first semiconductor region having afirst impurity concentration, and a second semiconductor region having asecond impurity concentration higher than the first impurityconcentration, the second semiconductor region extends along the thirdline to be widened on the second transfer region side, and the firstsemiconductor region is disposed on both sides of the secondsemiconductor region in a direction in which the second semiconductorregion is widened.

In the photoelectric conversion device according to one aspect of thepresent disclosure, the transfer part includes the first transfer regionconfigured to transfer electric charge along a first line, the secondtransfer region configured to transfer the electric charge along asecond line, and the third transfer region configured to transfer theelectric charge from the first transfer region side to the secondtransfer region side along a third line connected to the first line andthe second line, and the third line is deviated from at least one of thefirst line and the second line. Thereby, a direction of electric chargetransfer or the like is changed in at least the third transfer region.In the third transfer region, the second semiconductor region having thesecond impurity concentration higher than the first impurityconcentration extends along the third line to be widened on the secondtransfer region side, and the first semiconductor region having thefirst impurity concentration is disposed on both sides of the secondsemiconductor region in a direction in which the second semiconductorregion is widened. Thereby, an electric potential gradient (potentialenergy gradient) in which electric charge moves from the first transferregion side to the second transfer region side along the third line isformed in the third transfer region. Therefore, it is unnecessary todispose a large number of transfer electrodes on the third transferregion to change a direction of electric charge transfer or the like.Therefore, according to the photoelectric conversion device of oneaspect of the present disclosure, in such a case in which a direction ofelectric charge transfer or the like is changed in the transfer part,the electric charge can be reliably transferred while avoiding increasein the number of transfer electrodes.

In the photoelectric conversion device according to one aspect of thepresent disclosure, a direction in which the second transfer regiontransfers the electric charge along the second line may be differentfrom a direction in which the first transfer region transfers theelectric charge along the first line. According to this, a direction ofelectric charge transfer can be changed in the transfer part.

In the photoelectric conversion device according to one aspect of thepresent disclosure, the third line may be a curve. According to this, adirection of electric charge transfer can be smoothly changed in thetransfer part.

In the photoelectric conversion device according to one aspect of thepresent disclosure, the transfer part may further include a thirdtransfer electrode disposed on the third transfer region. According tothis, since not only electric potentials of the first transfer regionand the second transfer region but also an electric potential of thethird transfer region can be controlled, the electric charge can be morereliably transferred.

In the photoelectric conversion device according to one aspect of thepresent disclosure, the transfer part may further include a buried layerhaving a conductivity type different from conductivity types of thefirst semiconductor region and the second semiconductor region, and theburied layer may be disposed on the third transfer region. According tothis, since it is not necessary to dispose a transfer electrode on thethird transfer region, the configuration can be simplified. Also,generation of a dark current in the third transfer region can besuppressed.

The photoelectric conversion device according to one aspect of thepresent disclosure may further include a light-shielding layer disposedon an incident side of light with respect to the transfer part.According to this, unnecessary electric charge generated in the transferpart due to incidence of light on the transfer part can be prevented.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide aphotoelectric conversion device capable of reliably transferringelectric charge while avoiding increase in the number of transferelectrodes in such a case in which a direction of electric chargetransfer or the like is changed in a transfer part.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a photoelectric conversion device according toone embodiment.

FIG. 2 is a cross-sectional view of the photoelectric conversion devicealong line II-II illustrated in FIG. 1 .

FIG. 3 is a plan view of a transfer part illustrated in FIG. 1 .

FIG. 4 is a cross-sectional view of the transfer part along line IV-IVillustrated in FIG. 3 .

FIG. 5 is a cross-sectional view of the transfer part along line V-Villustrated in FIG. 3 .

FIG. 6 is a view for explaining a principle in which an electricpotential gradient is formed in a third transfer region illustrated inFIG. 3 .

FIG. 7 is a potential energy diagram of the transfer part illustrated inFIG. 3 .

FIG. 8 is a potential energy diagram of the transfer part illustrated inFIG. 3 .

FIG. 9 is a potential energy diagram of the transfer part illustrated inFIG. 3 .

FIG. 10 is a cross-sectional view of a photoelectric conversion deviceaccording to a modified example.

FIG. 11 is a cross-sectional view of a transfer part illustrated in FIG.10 .

FIG. 12 is a plan view of the transfer part of the modified example.

FIG. 13 is a cross-sectional view of the transfer part along lineXIII-XIII illustrated in FIG. 12 .

FIG. 14 is a cross-sectional view of the transfer part along lineXIV-XIV illustrated in FIG. 12 .

FIG. 15 is a plan view of the transfer part of the modified example.

FIG. 16 is a plan view of the transfer part of the modified example.

FIG. 17 is a plan view of the transfer part of the modified example.

FIG. 18 is a plan view of the transfer part of the modified example.

FIG. 19 is a plan view of the transfer part of the modified example.

FIG. 20 is a potential energy diagram of the transfer part illustratedin FIG. 12 .

FIG. 21 is a potential energy diagram of the transfer part illustratedin FIG. 12 .

FIG. 22 is a potential energy diagram of the transfer part illustratedin FIG. 12 .

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be describedin detail with reference to the drawings. Further, in each of thedrawings, the same or corresponding portions will be denoted by the samereference signs, and duplicate description thereof will be omitted.

[Configuration of Photoelectric Conversion Device]

As illustrated in FIGS. 1 and 2 , a photoelectric conversion device 1includes a semiconductor layer 2 and a wiring layer 3. A photoelectricconversion part 4 generating electric charge according to incidence oflight hv is provided in the semiconductor layer 2. As a transfer part 5for transferring electric charge, a vertical shift register 5 a, ahorizontal shift register 5 b, a corner register 5 c, and amultiplication register 5 d are provided in the semiconductor layer 2and the wiring layer 3. The photoelectric conversion device 1 is, forexample, a back-illuminated solid-state imaging device in which aCCD-type imaging region is configured by the photoelectric conversionpart 4 and the vertical shift register 5 a. Hereinafter, a thicknessdirection of the semiconductor layer 2 is referred to as a Z-axisdirection, one direction perpendicular to the Z-axis direction isreferred to as an X-axis direction, and a direction perpendicular toboth the Z-axis direction and the X-axis direction is referred to as aY-axis direction.

The semiconductor layer 2 includes a semiconductor substrate 21, asemiconductor layer 22, and a semiconductor region 23. The semiconductorsubstrate 21 is, for example, a P⁺-type silicon substrate. Thesemiconductor layer 22 is, for example, a P⁻-type silicon layer formedon a surface 21 a of the semiconductor substrate 21 by epitaxial growth.The semiconductor region 23 is, for example, an N⁺-type semiconductorregion formed in the semiconductor layer 22 along a surface 22 a of thesemiconductor layer 22 by being doped with N-type impurities.

Further, “P⁺-type” means that a concentration of P-type impurities ishigh such as, for example, a concentration of P-type impurities being1×10¹⁷ cm⁻³ or higher, and “P⁻-type” means that a concentration ofP-type impurities is low such as, for example, a concentration of P-typeimpurities being 1×10¹⁵ cm⁻³ or lower. The same applies to N-typeimpurities.

A recessed part 24 is formed on a back surface 21 b of the semiconductorsubstrate 21. The recessed part 24 is formed by, for example, etchingand has a truncated quadrangular pyramid shape that widens toward a sideof the semiconductor substrate 21 opposite to the surface 21 a side. Inthe photoelectric conversion device 1, a PN junction region formed in aportion of the semiconductor layer 22 corresponding to a bottom surface24 a of the recessed part 24 constitutes the photoelectric conversionpart 4.

A light-shielding layer 6 is formed on the back surface 21 b of thesemiconductor substrate 21 and a side surface 24 b of the recessed part24. The light-shielding layer 6 has an opening 6 a corresponding to thebottom surface 24 a of the recessed part 24. The light-shielding layer 6is, for example, a metal film formed on the back surface 21 b and theside surface 24 b by vapor deposition or sputtering. In thephotoelectric conversion device 1, the light hv is incident on thephotoelectric conversion part 4 from the back surface 21 b side of thesemiconductor substrate 21 via the opening 6 a of the light-shieldinglayer 6 and the bottom surface 24 a of the recessed part 24.

The wiring layer 3 is formed on the surface 22 a of the semiconductorlayer 22 with an insulating film 7 interposed therebetween. The wiringlayer 3 includes a plurality of transfer electrodes (not illustrated)and an interlayer insulating film 31. The insulating film 7 is, forexample, an SiO₂ film. The interlayer insulating film 31 is, forexample, a BPSG film.

The vertical shift register 5 a includes a plurality of transferelectrodes disposed at a portion of the wiring layer 3 corresponding tothe photoelectric conversion parts 4. The vertical shift register 5 atransfers electric charge generated in the photoelectric conversion part4 to one side in the Y-axis direction.

The horizontal shift register 5 b extends in the X-axis direction on oneside of the vertical shift register 5 a in the Y-axis direction. Thehorizontal shift register 5 b includes a plurality of transferelectrodes aligned in the X-axis direction. The horizontal shiftregister 5 b transfers the electric charge transferred by the verticalshift register 5 a to one side (left side in FIG. 1 ) in the X-axisdirection.

The corner register 5 c is disposed on one side of the horizontal shiftregister 5 b in the X-axis direction. The corner register 5 c transfersthe electric charge transferred by the horizontal shift register 5 b,and changes a direction of transferring the electric charge from oneside (left side in FIG. 1 ) to the other side (right side in FIG. 1 ) inthe X-axis direction.

The multiplication register 5 d extends in the X-axis direction on oneside of the horizontal shift register 5 b in the Y-axis direction. Themultiplication register 5 d includes a plurality of transfer electrodesaligned in the X-axis direction. The multiplication register 5 dmultiplies the electric charge (electrons) while transferring theelectric charge transferred by the corner register 5 c to the other side(right side in FIG. 1 ) in the X-axis direction. The electric chargetransferred by the multiplication register 5 d are output to the outsidethrough an amplifier formed in the semiconductor layer 22.

The horizontal shift register 5 b, the corner register 5 c, and themultiplication register 5 d are covered with a frame portion surroundingthe recessed part 24 of the semiconductor substrate 21 and thelight-shielding layer 6 when viewed from an incident side of the lighthv.

That is, in the photoelectric conversion device 1, the frame portion ofthe semiconductor substrate 21 and the light-shielding layer 6 aredisposed on the incident side of the light hv with respect to thehorizontal shift register 5 b, the corner register 5 c, and themultiplication register 5 d.

[Configuration of Transfer Part]

A configuration of a portion of the transfer part 5 corresponding to thecorner register 5 c will be described in detail with reference to FIGS.3, 4, and 5 . FIG. 3 is a plan view of the transfer part 5(specifically, a portion of the transfer part 5 corresponding to thecorner register 5 c) illustrated in FIG. 1 . FIG. 4 is a cross-sectionalview of the transfer part 5 along IV-IV line illustrated in FIG. 3 , andFIG. 5 is a cross-sectional view of the transfer part 5 along V-V lineillustrated in FIG. 3 .

As illustrated in FIGS. 3, 4, and 5 , the transfer part 5 includes afirst transfer region 51, a second transfer region 52, a third transferregion 53, a first transfer electrode 55, a second transfer electrode56, and a third transfer electrode 57. The first transfer region 51, thesecond transfer region 52, and the third transfer region 53 are formedin the semiconductor layer 22. The first transfer electrode 55, thesecond transfer electrode 56, and the third transfer electrode 57 areprovided in the wiring layer 3.

The first transfer region 51 and the first transfer electrode 55correspond to an end portion on a downstream side (downstream side in adirection of electric charge transfer) of the horizontal shift register5 b (see FIG. 1 ). The second transfer region 52 and the second transferelectrode 56 correspond to an end portion on an upstream side (upstreamside in the direction of electric charge transfer) of the multiplicationregister 5 d (see FIG. 1 ). The third transfer region 53 and the thirdtransfer electrode 57 correspond to the corner register 5 c.

The first transfer region 51 includes a semiconductor region 25 formedon one side of the semiconductor layer 22 in the Z-axis direction (aside opposite to the incident side of the light hv in the Z-axisdirection). The second transfer region 52 includes a semiconductorregion 26 formed on one side of the semiconductor layer 22 in the Z-axisdirection. The semiconductor region 25 and the semiconductor region 26are, for example, N⁺-type semiconductor regions formed in thesemiconductor layer 22 by being doped with N-type impurities.

The third transfer region 53 includes a first semiconductor region 27and a second semiconductor region 28 formed on one side of thesemiconductor layer 22 in the Z-axis direction. The first semiconductorregion 27 has a first impurity concentration. The second semiconductorregion 28 has a second impurity concentration higher than the firstimpurity concentration. The first semiconductor region 27 is, forexample, an N⁻-type semiconductor region formed in the semiconductorlayer 22 by being doped with N-type impurities. The second semiconductorregion 28 is, for example, an N-type semiconductor region formed in thesemiconductor layer 22 by being doped with N-type impurities.

An end portion of the third transfer region 53 on an upstream side ofthe first semiconductor region 27 and the second semiconductor region 28is connected to an end portion of the first transfer region 51 on adownstream side of the semiconductor region 25. An end portion of thethird transfer region 53 on a downstream side of the first semiconductorregion 27 and the second semiconductor region 28 is connected to an endportion of the second transfer region 52 on an upstream side of thesemiconductor region 26. Further, in the transfer part 5, a P⁺⁺-typesemiconductor region 29 in which a concentration of P-type impurities ishigher than that of the P⁺ type is formed around the semiconductorregion 25, the semiconductor region 26, the first semiconductor region27, and the second semiconductor region 28.

The first transfer electrode 55 is disposed on one side of the firsttransfer region 51 in the Z-axis direction. That is, the first transferelectrode 55 is disposed on the first transfer region 51. The secondtransfer electrode 56 is disposed on one side of the second transferregion 52 in the Z-axis direction. That is, the second transferelectrode 56 is disposed on the second transfer region 52. The thirdtransfer electrode 57 is disposed on one side of the third transferregion 53 in the Z-axis direction. That is, the third transfer electrode57 is disposed on the third transfer region 53. The first transferelectrode 55, the second transfer electrode 56, and the third transferelectrode 57 are electrically separated by the interlayer insulatingfilm 31. The first transfer electrode 55, the second transfer electrode56, and the third transfer electrode 57 are formed of, for example,polysilicon.

As illustrated in FIG. 3 , the first transfer region 51 transferselectric charge to one side (left side in FIG. 3 ) in the X-axisdirection along a first line L1. The first line L1 is a straight lineextending in the X-axis direction. The second transfer region 52transfers electric charge to the other side (right side in FIG. 3 ) inthe X-axis direction along a second line L2. The second line L2 is astraight line extending in the X-axis direction. A direction in whichthe second transfer region 52 transfers electric charge along the secondline L2 is different from a direction in which the first transfer region51 transfers electric charge along the first line L1. In thephotoelectric conversion device 1, the direction in which the secondtransfer region 52 transfers electric charge along the second line L2and the direction in which the first transfer region 51 transferselectric charge along the first line L1 form an angle of 180 degrees.

A third line L3 is deviated from both the first line L1 and the secondline L2. That is, the third line L3 is deviated from the first line L1and is deviated from the second line L2. Here, “the third line L3 isdeviated from the first line L1” means that at least a part of the thirdline L3 is not positioned on an extension line of the first line L1extending from a downstream end of the first line L1 (on a tangent lineextending from the downstream end of the first line L1 if the first lineL1 is a curve). Also, “the third line L3 is deviated from the secondline L2” means that at least a part of the third line L3 is notpositioned on an extension line of the second line L2 extending from anupstream end of the second line L2 (on a tangent line extending from theupstream end of the second line L2 if the second line L2 is a curve). Inthe photoelectric conversion device 1, the entire third line L3 is notpositioned on the extension line of the first line L1 extending from thedownstream end of the first line L1, and the entire third line L3 is notpositioned on the extension line of the second line L2 extending fromthe upstream end of the second line L2.

The second line L2 is deviated from the first line L1. Here, “the secondline L2 is deviated from the first line L1” means that at least a partof the second line L2 is not positioned on the extension line of thefirst line L1 extending from the downstream end of the first line L1 (ona tangent line extending from the downstream end of the first line L1 ifthe first line L1 is a curve). In the photoelectric conversion device 1,the entire second line L2 is not positioned on the extension line of thefirst line L1 extending from the downstream end of the first line L1.

The third transfer region 53 transfers electric charge from the firsttransfer region 51 side to the second transfer region 52 side along thethird line L3 connected to the first line L1 and the second line L2.That is, the third transfer region 53 changes a direction of electriccharge transfer from one side (left side in FIG. 3 ) to the other side(right side in FIG. 3 ) in the X-axis direction. The third line L3 is acurve (for example, an arcuate curve) connected to the first line L1 andthe second line L2. In the photoelectric conversion device 1, the firstline L1 and the third line L3 has a relationship in which they are incontact with each other, and the second line L2 and the third line L3has a relationship in which they are in contact with each other.

A configuration of the third transfer region 53 will be described inmore detail. As illustrated in FIG. 3 , the second semiconductor region28 extends along the third line L3 to be widened on the second transferregion 52 side. In the photoelectric conversion device 1, a width of thesecond semiconductor region 28 in a normal direction of the third lineL3 increases as the second semiconductor region 28 comes closer to thesecond transfer region 52 (in other words, with distance away from thefirst transfer region 51). The third line L3 passes through, forexample, a center in a width direction of the second semiconductorregion 28. The first semiconductor region 27 is disposed on both sidesof the second semiconductor region 28 in a direction in which the secondsemiconductor region 28 is widened (that is, a width direction of thesecond semiconductor region 28 in the normal direction of the third lineL3). Further, a width of the second semiconductor region 28 in thenormal direction of the third line L3 may increase continuously or mayincrease in stages.

In the third transfer region 53 configured as described above, anelectric potential gradient (potential energy gradient) in whichelectric charge moves from the first transfer region 51 side to thesecond transfer region 52 side is formed along the third line L3. Aprinciple thereof is as follows. That is, in a portion of the thirdtransfer region 53 close to the first transfer region 51, since a widthof the second semiconductor region 28 with respect to a width of thethird transfer region 53 is small as shown in (a) of FIG. 6 , fringingfrom the first semiconductor regions 27 on both sides is strong, and anelectric potential thereof (the solid line illustrated in (a) of FIG. 6) is shallow. On the other hand, in a portion of the third transferregion 53 close to the second transfer region 52, since a width of thesecond semiconductor region 28 with respect to the width of the thirdtransfer region 53 is large as shown in (b) of FIG. 6 , fringing fromthe first semiconductor regions 27 on both sides is weak, and anelectric potential thereof (the solid line illustrated in (b) of FIG. 6) is deep. As described above, in the third transfer region 53, thesecond semiconductor region 28 extends along the third line L3 to bewidened on the second transfer region 52 side. Therefore, in the thirdtransfer region 53, an electric potential gradient in which electriccharge moves from the first transfer region 51 side to the secondtransfer region 52 side is formed along the third line L3. Further, thebroken lines illustrated in (a) and (b) of FIG. 6 each indicate anelectric potential when the first semiconductor region 27 and the secondsemiconductor region 28 each exist alone.

Transfer of electric charge in a portion of the transfer part 5corresponding to the corner register 5 c will be described withreference to FIGS. 7, 8, and 9 . FIGS. 7, 8, and 9 are potential energydiagrams of the transfer part 5 illustrated in FIG. 3 (specifically, aportion of the transfer part 5 corresponding to the corner register 5c). Further, in the present description, a transfer region adjacent toan upstream side of the first transfer region 51 is referred to as atransfer region 61, and a transfer region adjacent to a downstream sideof the second transfer region 52 is referred to as a transfer region 62.Also, a transfer electrode disposed on the transfer region 61 isreferred to as a transfer electrode 63, and a transfer electrodedisposed on the transfer region 62 is referred to as a transferelectrode 64.

First, from a state in which a low voltage is applied to the transferelectrode 63 and the second transfer electrode 56, a high voltage isapplied to the first transfer electrode 55 and the transfer electrode64, and a high voltage is applied to the third transfer electrode 57 asshown in (a) of FIG. 7 , a low voltage is applied to the first transferelectrode 55 and the transfer electrode 64 as shown in (b) and (c) ofFIG. 7 . Thereby, potential energies of the first transfer region 51 andthe transfer region 62 become shallow, a potential energy of thetransfer region 61 serves as a barrier, and thereby electric charge(electrons) moves from the first transfer region 51 to the thirdtransfer region 53. At this time, since an electric potential gradient(potential energy gradient) in which electric charge moves from thefirst transfer region 51 side to the second transfer region 52 side isformed in the third transfer region 53, the electric charge moves to thesecond transfer region 52 side in the third transfer region 53. Also, apotential energy of the second transfer region 52 serves as a barrier,and electric charge moves from the transfer region 62 to a transferregion (not shown) on a downstream side. Further, (b) of FIG. 7 shows astate in which the potential energies of the first transfer region 51and the transfer region 62 are in the process of transition.

Next, a high voltage is applied to the transfer electrode 63 and thesecond transfer electrode 56 as shown in (a) of FIG. 8 . Thereby,potential energies of the transfer region 61 and the second transferregion 52 become deeper, and electric charge moves from the thirdtransfer region 53 to the second transfer region 52. Also, electriccharge moves from a transfer region on an upstream side (not shown) tothe transfer region 61. Next, a low voltage is applied to the thirdtransfer electrode 57 as shown in (b) of FIG. 8 . Thereby, a potentialenergy of the third transfer region 53 becomes shallow. Next, a highvoltage is applied to the first transfer electrode 55 and the transferelectrode 64 as shown in (c) of FIG. 8 . Thereby, the potential energiesof the first transfer region 51 and the transfer region 62 becomedeeper.

Next, a low voltage is applied to the transfer electrode 63 and thesecond transfer electrode 56 as shown in (a) and (b) of FIG. 9 .Thereby, the potential energies of the transfer region 61 and the secondtransfer region 52 become shallow, the potential energy of the thirdtransfer region 53 serves as a barrier, and thereby electric chargemoves from the second transfer region 52 to the transfer region 62.Also, a potential energy of the transfer region on the upstream sideserves as a barrier, and electric charge moves from the transfer region61 to the first transfer region 51. Further, (a) of FIG. 9 shows a statein which the potential energies of the transfer region 61 and the secondtransfer region 52 are in the process of transition. Next, a highvoltage is applied to the third transfer electrode 57 as illustrated in(c) of FIG. 9 . Thereby, the potential energy of the third transferregion 53 becomes deeper, thereby returning to the state shown in (a) ofFIG. 7 .

[Operation and Effects]

In the photoelectric conversion device 1, the transfer part 5(specifically, a portion of the transfer part 5 corresponding to thecorner register 5 c) includes the first transfer region 51 configured totransfer electric charge along the first line L1, the second transferregion 52 configured to transfer electric charge along the second lineL2, and the third transfer region 53 configured to transfer electriccharge from the first transfer region 51 side to the second transferregion 52 side along the third line L3 connected to the first line L1and the second line L2, in which the third line L3 is deviated from boththe first line L1 and the second line L2. Thereby, a direction ofelectric charge transfer or the like is changed in at least the thirdtransfer region 53. In the third transfer region 53, the secondsemiconductor region 28 having the second impurity concentration higherthan the first impurity concentration extends along the third line L3 tobe widened on the second transfer region 52 side, and the firstsemiconductor region 27 having the first impurity concentration isdisposed on both sides of the second semiconductor region 28 in adirection in which the second semiconductor region 28 is widened.Thereby, an electric potential gradient (potential energy gradient) inwhich electric charge moves from the first transfer region 51 side tothe second transfer region 52 side along the third line L3 is formed inthe third transfer region 53. Therefore, it is unnecessary to dispose alarge number of transfer electrodes on the third transfer region 53 tochange a direction of electric charge transfer or the like. Therefore,according to the photoelectric conversion device 1, in such a case inwhich a direction of electric charge transfer or the like is changed inthe transfer part 5, the electric charge can be reliably transferredwhile avoiding increase in the number of transfer electrodes.

In the photoelectric conversion device 1, since increase in the numberof transfer electrodes can be avoided in the transfer part 5, thefollowing specific effects are obtained. That is, decrease in yield dueto a structure thereof becoming complicated can be prevented. Also,high-speed driving being hindered due to increase in electrical capacitycan be prevented. Further, increase in power consumption can beprevented.

In the photoelectric conversion device 1, a direction in which thesecond transfer region 52 transfers electric charge along the secondline L2 is different from a direction in which the first transfer region51 transfers electric charge along the first line L1. Thereby, adirection of electric charge transfer can be changed in the transferpart 5.

In the photoelectric conversion device 1, the third line L3 is a curve.Thereby, a direction of electric charge transfer can be smoothly changedin the transfer part 5.

In the photoelectric conversion device 1, the transfer part 5 includesthe third transfer electrode 57 disposed on the third transfer region53. Thereby, since not only electric potentials of the first transferregion 51 and the second transfer region 52 but also an electricpotential of the third transfer region 53 can be controlled, theelectric charge can be more reliably transferred.

In the photoelectric conversion device 1, the light-shielding layer 6 isdisposed on the incident side of the light hv with respect to thetransfer part 5. Thereby, unnecessary electric charge generated in thetransfer part 5 due to incidence of the light hv on the transfer part 5can be prevented.

Modified Example

The present disclosure is not limited to the embodiment described above.For example, the photoelectric conversion device 1 may be afront-illuminated solid-state imaging device as illustrated in FIG. 10 .In the photoelectric conversion device 1 illustrated in FIG. 10 , asemiconductor region 23 is formed in a semiconductor layer 22 along asurface 22 a of the semiconductor layer 22, and an insulating film 7, awiring layer 3, and a light-shielding layer 6 are disposed on thesurface 22 a of the semiconductor layer 22 in that order. In thephotoelectric conversion device 1 illustrated in FIG. 10 , light hv isincident on a photoelectric conversion part 4 from the surface 22 a sideof the semiconductor layer 22 via an opening 6 a of the light-shieldinglayer 6, the wiring layer 3, and the insulating film 7. Thephotoelectric conversion device 1 illustrated in FIG. 10 includes atransfer part 5 illustrated in FIG. 11 . The transfer part 5 illustratedin FIG. 11 is different from the transfer part 5 illustrated in FIG. 4in that a first transfer electrode 55, a second transfer electrode 56,and a third transfer electrode 57 are disposed on an incident side ofthe light hv with respect to a first transfer region 51, a secondtransfer region 52, and a third transfer region 53. Further, FIG. 11 isa cross-sectional view along a line similar to that of FIG. 4 (that is,along a line IV-IV illustrated in FIG. 3 ).

Also, in the photoelectric conversion device 1 illustrated in FIGS. 1and 2 , the semiconductor substrate 21 may be made thin in its entirety.In that case, the photoelectric conversion device 1 may further includea support substrate disposed on a side opposite to the incident side ofthe light hv with respect to the wiring layer 3.

Also, in the photoelectric conversion device 1 illustrated in FIGS. 1and 2 , in a case in which the frame portion of the semiconductorsubstrate 21 surrounding the recessed part 24 is disposed on theincident side of the light hv with respect to the horizontal shiftregister 5 b, the corner register 5 c, and the multiplication register 5d, the photoelectric conversion device 1 may not include thelight-shielding layer 6. This is because, when the semiconductorsubstrate 21 includes the frame portion, even if the light hv isincident on the frame portion and electric charge is generated in theframe portion, there is a high likelihood that the electric charge willdisappear before reaching the semiconductor layer 22.

Also, the transfer part 5 may not include a transfer electrode disposedon the third transfer region 53 (a transfer electrode corresponding tothe third transfer electrode 57 described above). The transfer part 5illustrated in FIGS. 12, 13, and 14 is different from the transfer part5 illustrated in FIG. 11 in that the transfer electrode is not disposedon the third transfer region 53, and a buried layer 54 is disposed onthe third transfer region 53. In the transfer part 5 illustrated inFIGS. 12, 13, and 14 , the buried layer 54 is disposed on one side ofthe third transfer region 53 in the Z-axis direction (incident side ofthe light hv in the Z-axis direction). That is, the buried layer 54 isdisposed on the third transfer region 53. The buried layer 54 has aconductivity type different from conductivity types of a firstsemiconductor region 27 and a second semiconductor region 28. The buriedlayer 54 is, for example, a P⁺-type semiconductor region formed in thesemiconductor layer 22 along the surface 22 a of the semiconductor layer22 by being doped with P-type impurities. According to the transfer part5 illustrated in FIGS. 12, 13 , and 14, since it is not necessary todispose a transfer electrode on the third transfer region 53, aconfiguration thereof can be simplified. Also, generation of a darkcurrent in the third transfer region 53 can be suppressed.

Also, when the transfer part 5 also functions as a photoelectricconversion part, the light-shielding layer 6 may not be disposed on aside of the transfer part 5 on which the light hv is incident regardlessof whether or not the transfer part 5 has the third transfer electrode57, and furthermore, regardless of whether or not the transfer part 5has the buried layer 54.

Also, a direction in which the second transfer region 52 transferselectric charge along a second line L2 need only be different from adirection in which the first transfer region 51 transfers electriccharge along a first line L1. For example, as illustrated in FIG. 15 ,the direction in which the second transfer region 52 transfers electriccharge along the second line L2 and the direction in which the firsttransfer region 51 transfers electric charge along the first line L1 mayform an angle of 90 degrees. As illustrated in FIG. 16 , the directionin which the second transfer region 52 transfers electric charge alongthe second line L2 and the direction in which the first transfer region51 transfers electric charge along the first line L1 may form an angleof 45 degrees.

Also, as illustrated in FIG. 17 , the first transfer region 51, thethird transfer region 53, the second transfer region 52, the thirdtransfer region 53, and the second transfer region 52 may be aligned inthat order from an upstream side. In this case, for the third transferregion 53 on a downstream side, the second transfer region 52 adjacent,on an upstream side, to the third transfer region 53 on the downstreamside corresponds to the first transfer region 51.

Also, if a third line L3 is deviated from at least one of the first lineL1 and the second line L2, the direction in which the second transferregion 52 transfers electric charge along the second line L2 may be thesame as the direction in which the first transfer region 51 transferselectric charge along the first line L1 as illustrated in FIG. 18 .According to such a configuration, in such a case in which a transferpath of electric charge is changed in the transfer part 5, the electriccharge can be reliably transferred while avoiding increase in the numberof transfer electrodes.

Also, if the third line L3 is deviated from at least one of the firstline L1 and the second line L2, the second line L2 may not be deviatedfrom the first line L1 as illustrated in FIG. 19 . In the transfer part5 illustrated in FIG. 19 , the first line L1 and the second line L2 arepositioned on the same straight line, and the third line L3 extends todeviate from the straight line and then return to the straight line.According to such a configuration, for example, in a case in which anobject to be avoided by the transfer part 5 exists between the firsttransfer region 51 and the second transfer region 52, and the transferpart 5 cannot be formed linearly, the electric charge can be reliablytransferred while avoiding increase in the number of transferelectrodes.

Also, transfer of electric charge at a portion of the transfer part 5corresponding to a corner register 5 c may be performed in a state inwhich a potential energy of the third transfer region 53 is fixedregardless of whether or not the transfer part 5 has the third transferelectrode 57. A specific example thereof will be described withreference to FIGS. 20, 21, and 22 . FIGS. 20, 21, and 22 are potentialenergy diagrams of the transfer part 5 illustrated in FIG. 12(specifically, a portion of the transfer part 5 corresponding to thecorner register 5 c). Further, in the present description, a transferregion adjacent to an upstream side of the first transfer region 51 isreferred to as a transfer region 61, and a transfer region adjacent to adownstream side of the second transfer region 52 is referred to as atransfer region 62. Also, a transfer electrode disposed on the transferregion 61 is referred to as a transfer electrode 63, and a transferelectrode disposed on the transfer region 62 is referred to as atransfer electrode 64.

First, from a state in which a low voltage is applied to the transferelectrode 63 and the second transfer electrode 56 and a high voltage isapplied to the first transfer electrode 55 and the transfer electrode 64(in this state, a potential energy of the third transfer region 53 isdeeper than potential energies of the transfer region 61 and the secondtransfer region 52 and shallower than potential energies of the firsttransfer region 51 and the transfer region 62) as shown in (a) of FIG.20 , a low voltage is applied to the first transfer electrode 55 and thetransfer electrode 64 as shown in (b) and (c) of FIG. 20 . Thereby, thepotential energies of the first transfer region 51 and the transferregion 62 become shallow, a potential energy of the transfer region 61serves as a barrier, and electric charge (electrons) moves from thefirst transfer region 51 to the third transfer region 53. At this time,since an electric potential gradient (potential energy gradient) inwhich electric charge moves from the first transfer region 51 side tothe second transfer region 52 side is formed in the third transferregion 53, the electric charge moves to the second transfer region 52side in the third transfer region 53. Also, the potential energy of thesecond transfer region 52 serves as a barrier, and electric charge movesfrom the transfer region 62 to a transfer region (not shown) on adownstream side. Further, (b) of FIG. 20 shows a state in which thepotential energies of the first transfer region 51 and the transferregion 62 are in the process of transition.

Next, a high voltage is applied to the transfer electrode 63 and thesecond transfer electrode 56 as shown in (a) of FIG. 21 . Thereby, thepotential energies of the transfer region 61 and the second transferregion 52 become deeper, and electric charge moves from the thirdtransfer region 53 to the second transfer region 52. Also, electriccharge moves from a transfer region on an upstream side (not shown) tothe transfer region 61. Next, a high voltage is applied to the firsttransfer electrode 55 and the transfer electrode 64 as shown in (b) ofFIG. 21 . Thereby, the potential energies of the first transfer region51 and the transfer region 62 become deeper. Next, a low voltage isapplied to the transfer electrode 63 and the second transfer electrode56, as illustrated in (a) and (b) of FIG. 22 . Thereby, the potentialenergies of the transfer region 61 and the second transfer region 52become shallow, thereby returning to the state shown in (a) of FIG. 20 .Further, (a) of FIG. 22 shows a state in which the potential energies ofthe transfer region 61 and the second transfer region 52 are in theprocess of transition. In the process of this transition, the potentialenergy of the third transfer region 53 serves as a barrier, and therebyelectric charge moves from the second transfer region 52 to the transferregion 62. Also, a potential energy of the transfer region on theupstream side serves as a barrier, and electric charge moves from thetransfer region 61 to the first transfer region 51.

Also, in any of the embodiment and the example described above, an endportion of the third transfer region 53 on an upstream side of thesecond semiconductor region 28 may be slightly separated (to such anextent that transfer of electric charge is not hindered) from an endportion of the first transfer region 51 on a downstream side of thesemiconductor region 25. Also, in any of the embodiment and the exampledescribed above, an end portion of the third transfer region 53 on adownstream side of the second semiconductor region 28 may be slightlyseparated (to such an extent that transfer of electric charge is nothindered) from an end portion of the second transfer region 52 on anupstream side of the semiconductor region 26. Also, in any of theembodiment and the example described above, conductivity types of theP-type and N-type may be reversed with respect to those described above.Also, in any of the embodiment and the example described above, aconcentration of impurities in each of the semiconductor regions is notlimited to those described above, and can be changed as appropriate.

REFERENCE SIGNS LIST

-   -   1 Photoelectric conversion device    -   4 Photoelectric conversion part    -   5 Transfer part    -   6 Light-shielding layer    -   27 First semiconductor region    -   28 Second semiconductor region    -   51 First transfer region    -   52 Second transfer region    -   53 Third transfer region    -   54 Buried layer    -   55 First transfer electrode    -   56 Second transfer electrode    -   57 Third transfer electrode    -   L1 First line    -   L2 Second line    -   L3 Third line

1: A photoelectric conversion device comprising: a photoelectricconversion part configured to generate electric charge according toincidence of light; and a transfer part configured to transfer theelectric charge, wherein the transfer part includes: a first transferregion configured to transfer the electric charge along a first line; asecond transfer region configured to transfer the electric charge alonga second line; a third transfer region configured to transfer theelectric charge from the first transfer region side to the secondtransfer region side along a third line connected to the first line andthe second line; a first transfer electrode disposed on the firsttransfer region; and a second transfer electrode disposed on the secondtransfer region, the third line is deviated from at least one of thefirst line and the second line, the third transfer region includes: afirst semiconductor region having a first impurity concentration; and asecond semiconductor region having a second impurity concentrationhigher than the first impurity concentration, the second semiconductorregion extends along the third line to be widened on the second transferregion side, and the first semiconductor region is disposed on bothsides of the second semiconductor region in a direction in which thesecond semiconductor region is widened. 2: The photoelectric conversiondevice according to claim 1, wherein a direction in which the secondtransfer region transfers the electric charge along the second line isdifferent from a direction in which the first transfer region transfersthe electric charge along the first line. 3: The photoelectricconversion device according to claim 1, wherein the third line is acurve. 4: The photoelectric conversion device according to claim 1,wherein the transfer part further includes a third transfer electrodedisposed on the third transfer region. 5: The photoelectric conversiondevice according to claim 1, wherein the transfer part further includesa buried layer having a conductivity type different from conductivitytypes of the first semiconductor region and the second semiconductorregion, and the buried layer is disposed on the third transfer region.6: The photoelectric conversion device according to claim 1, furthercomprising a light-shielding layer disposed on an incident side of thelight with respect to the transfer part.